Free, vascularized bone grafts have been recently reported in limited clinical applications. This investigation is proposed to develop an experimental quantitative model to delineate the rates and pattern of repair in free, vascularized, canine, segmental, fibular, autogenous, cortical bone grafts. The biological and physical aspects of repair will be correlated. Patency of anastomoses will be determined by bone scan and arteriography. The graft reparative processes will be quantitated by continuous tetracycline labelling, microradiography, radiography, and torsional loading to failure.